The present invention relates to a sintered sputtering target containing two or more types of refractory metals which is capable of improving the target structure to prevent the dropout of metal particles other than the matrix-forming major component, and improving the deposition quality by eliminating the generation of arcing and particles in sputtering.
Since ruthenium (Ru), rhodium (Rh) and iridium (Ir) as refractory metals have superior thermal stability, and also possess superior low resistivity and barrier properties, they are attracting attention as a deposition material of semiconductor devices, and particularly as a gate electrode material and various diffusion barrier materials.
Although ruthenium (Ru), rhodium (Rh) and iridium (Ir) are sometimes used independently as a thin film or as a target material for forming such a thin film, there is a problem in that the wettability during the plating process is inferior.
Thus, in order to overcome this drawback, proposals have been made to add other metals (in particular refractory metals) to the three metals of ruthenium (Ru), rhodium (Rh) and iridium (Ir).
The well known sputtering method is generally used as the means for forming a thin film. A radio frequency (RF) sputtering device is used as the sputtering method. The manufacture of an alloy target of the foregoing composition is essential when performing sputtering. In addition, improving the target quality is extremely important in order to improve the deposition quality.
Although the method of melting and plastic working can be considered when manufacturing a target by adding a refractory metal to ruthenium (Ru), rhodium (Rh) or iridium (Ir) as the refractory metal, since ruthenium, rhodium, and iridium have high melting points and are fragile materials, the melter is extremely expensive and plastic working also requires special skills. Thus, there is a problem in that the manufacturing cost becomes high.
In view of the above, it is suitable to use the sintering method for manufacturing a target. Nevertheless, even when manufacturing a sintered compact from two or more types of refractory metals, it is not necessarily easy to improve the quality of the target.
If the content of alloy elements as the minor component in ruthenium (Ru), rhodium (Rh) or iridium (Ir) as the refractory metal is low, then this will not become a significant problem. Nevertheless, if the additive amount of alloy to become the minor component is increased, metals as the minor component will exist in dots (island shape) in the structure (matrix component) as the major component, and these will drop out in sputtering and generate particles.
Since holes are formed after the dropout and irregular edges are formed in the vicinity of such holes, these will cause the generation of abnormal discharge in sputtering, and cause a problem of generating even more particles. In order to improve the quality of deposition, there are strong demands for eliminating the generation of such particles.
Gas components or other impurities existing in the target are also easily collected at the interface of the structure, and the existence of these impurities also causes the generation of arcing and particles in sputtering. Thus, there is a problem in that the sintering density will deteriorate and weaken the target strength and lower the deposition quality.
Although the following explanation does not directly relate to the target of the present invention, proposals concerning measures for preventing the generation of particles and cracks in the target (improvement of bending strength) that have been made in connection with refractory metal targets are now explained for reference.
A molybdenum-tungsten target having a bending strength of 750 Mpa composed primarily of molybdenum and tungsten, wherein the structure is achieved by sintering molybdenum particles and tungsten particles with a diffusion bonding distance of 1.0 μm or less (refer to Patent Document 1).
A manufacturing method of a tungsten-titanium target material for preventing the generation of particles and which is used for obtaining a sintered compact having an average grain size of 50 μm or less, wherein mixed powder of tungsten powder and titanium powder is subject to pressure sintering at 1500 to 1700° C., and comprising a structure composed of a titanium-tungsten alloy phase, a tungsten phase, and a titanium phase having an area ratio of 20% or greater in the target cross section (refer to Patent Document 2).
A Ta target for forming a barrier film capable of preventing the generation of particles obtained by sintering one or two or more types of powder (C, B, Ir, W, Ge, CeO2, RuO2) of 49 at % or less and Ta powder of 51 at % or more (refer to Patent Document 3).    [Patent Document 1] Japanese Patent Laid-Open Publication No.H11-36067    [Patent Document 2] Japanese Patent Laid-Open Publication No.H5-156384    [Patent Document 3] Japanese Patent Laid-Open Publication No.2000-355761